The present invention relates in general to optical imaging systems and in particular to an optical imaging field splitting system adapted to simultaneously and adjustably view two or more different images or object scenes and/or to simultaneously view the same image from two or more different angles.
A typical prior art optical image field splitting system uses some form of standard beam splitters to provide views of two or more images or object scenes superimposed on the same area of a single image plane. It is an inherent property of such prior art systems that each image will obscure or interfere with the other images. In order to circumvent this problem, prior art optical image field splitting systems use some mechanism for allowing projection of only a single view at a time onto the image plane. Methods of accomplishing such a result are many and varied. Typically, these methods include alternating shutters, mechanical scanning of a mirror or mirrors, and polarization state changing electro-optic devices. In any case, these methods do not allow a true simultaneous view since there is some finite time interval between the alternate views. This can have important consequences, particularly when comparing or inspecting rapidly changing but different scenes.
Additionally, prior art optical image field splitting systems typically do not allow for adjustment of the direction or position of the images or object scenes without changing the optical path length of the imaging system. Such a path length change inherently changes the system magnification and degree of image focus unless otherwise corrected. Another problem with prior art optical image field splitting systems that allow adjustment of the direction of the object scenes is the reduction of the angular field of view due to the reduced useable area of the field splitting mirror. Such a problem is illustrated in the optical image field splitting system described and illustrated in U.S. Pat. No. 4,167,756 to Smith.